The partnership would create a nationwide wireless network using WiMax technology, which is designed to provide high-speed Web access from laptops, cellphones and other mobile devices, as well as high-quality mobile video. Sprint and Clearwire have been working for months to cooperate on a WiMax rollout and are now trying to raise at least $3 billion for a joint venture.

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Under the plan the parties are reviewing, Comcast -- the largest cable operator with 24 million subscribers -- would put as much as $1 billion into the venture, with No. 2 operator Time Warner Cable adding $500 million. The sixth-biggest cable operator, Bright House Networks, is also involved in the talks and would contribute between $100 million and $200 million, people familiar with the matter said. Comcast Chief Executive Brian Roberts has played a prominent role in the talks.

Sprint, of Overland Park, Kan., and Clearwire, a Kirkland, Wash., start-up founded by wireless pioneer Craig McCaw, are trying to line up other funding too. Intel Corp.INTC0.14% has signaled a willingness to put in about $1 billion or more, depending on the terms, people familiar with the discussion say. And Google Inc. could provide hundreds of millions of dollars, the people say. The exact amount each would contribute could change, and people involved in the discussions said it is still possible the entire deal could fall through. Google and Intel both declined to comment.

Entering the wireless business is becoming a bigger priority for cable companies as they compete fiercely for customers with telecom giants AT&T Inc.T-0.17% and Verizon Communications Inc.VZ0.26% Those phone companies have encroached on cable's turf by entering the pay-TV business and are positioning themselves to offer a "quadruple play" of services that includes landline phone, high-speed Web access, cellphone, and video. "That's obviously a concern, if Verizon can put together a converged service offering that starts to peel people away from cable operators," said Mark Rowland, head of the wireless practice at IBB Consulting.

Cable companies' push into wireless would mark the next chapter in that escalating rivalry. It isn't clear precisely what wireless services the cable operators intend to offer via the WiMax venture. Executives at some of the operators feel the U.S. wireless market is already crowded, with 80% of U.S. consumers already owning a cellphone.

The companies are likely to try to distinguish themselves with advanced mobile data and video services that take advantage of the stockpiles of content they are already adept at licensing. People familiar with the discussions said some cable companies are looking at options to develop their own mobile devices in partnerships with manufacturers.

Sprint CEO Dan Hesse is pressing all parties to wrap up discussions in time for the wireless industry's trade show next week in Las Vegas, so Sprint can have something to present to investors. In addition to the $3 billion Sprint and Clearwire are trying to raise now to start rolling out WiMax, they will likely need more to complete a nationwide network. Sprint previously had told Wall Street the venture would cost $5 billion by 2010.

Mr. Hesse wants Sprint to begin building the WiMax network quickly so it can get a head-start over competitors AT&T and Verizon Wireless on advanced wireless broadband services. WiMax promises faster speeds than current technologies and a wider range of video and other services.

In exchange for funding the WiMax joint venture, the cable companies would get equity in the business and would be able to purchase wholesale access to the network to offer their own high-speed wireless data and voice services to customers, the people familiar with the discussions said.

The cable industry has been flirting with the idea of getting into wireless for years, but hasn't had a clear strategy. Investors have also discouraged cable companies from embarking on any big spending projects. A consortium of cable operators including Comcast, Time Warner Cable, Bright House Networks and Cox Communications Inc. bought more than $2 billion in radio spectrum in a 2006 government auction but never put it to use.

The same companies created a separate joint venture with Sprint in 2005, dubbed Pivot, that offered cellphone service in about 30 markets by the time it stopped marketing late last year amid low demand. One key problem was that cable providers didn't have significant control over pricing and marketing. They are asking for that control in the new WiMax venture. Comcast and other cable operators have also mulled acquiring a major wireless carrier.

Cox, the third-biggest cable operator, appears to be pursuing a separate wireless push. It acquired 22 radio spectrum licenses for $305 million last week, which would allow Cox to offer wireless service in its markets, predominantly in the south and southwest.

If cable operators dive into wireless, that will put more pressure on satellite TV providers, their other major competitors, to do the same. Satellite providers on their own can't offer high-speed Web access or voice services. Dish Network Corp.DISH-0.57% took a step into the wireless business through the FCC auction, winning 168 licenses throughout the country for $712 million. DirecTV Group Inc. hasn't announced any plans in wireless.

"This is like a game of three dimensional chess because the cable operators aren't just thinking about how this helps them compete with Verizon and AT&T, but how this helps them block potential threats from DirecTV and Dish," says Bernstein analyst Craig Moffett.

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